For individual injection for each cylinder of a multi-cylinder internal combustion engine, there are essentially two methods known, namely that of central injection and that of sequential injection into one intake-pipe portion for each cylinder. In the case of central injection, the distance between the common intake pipe and the individual cylinders is relatively long. In a four-stroke, four-cylinder engine with the induction-stroke sequence 1, 3, 4, 2, the fuel quantity to be drawn in by the first cylinder is already injected during the induction stroke for the fourth cylinder. The entire induction stroke for the second cylinder then follows, until finally the first cylinder draws in the fuel quantity injected for it into the intake pipe. By means of the beginning and length of the injection pulses it is possible to apportion the fuel quantities to the individual cylinders to some extent individually. Such a method is described in U.S. Pat. No. 4,301,780.
Very precise individual metering of fuel quantities to individual cylinders is possible with sequential injection. Here, an injection valve is allocated to each cylinder and this valve is activated separately.
In addition to the fuel quantities, the air quantities must also be adjusted. In the most widely used methods, the air quantity is adjusted by the throttle flap being adjusted directly by actuating the accelerator pedal. In more modern methods involving a so-called electronic accelerator pedal, such direct coupling is absent; rather, the accelerator-pedal signal is converted into an actuating signal for an actuator for the throttle flap. In such methods, the throttle flap is likewise adjusted directly upon actuation of the accelerator pedal but the extent of the adjustment of the throttle flap depends not only on the angle of the accelerator pedal but also on the current values of specified operating parameters. In a further-reaching proposal in U.S. Pat. No. 4,883,035, an offset between the actuation of the accelerator pedal and the adjustment of the throttle flap is additionally provided. This method is based on the realization that the adjustment of the throttle flap during an induction stroke leads to unfavorable driving performance in the case of an internal combustion engine with central injection. An adjustment of the accelerator pedal thus does not lead directly to an adjustment of the throttle flap; rather, after a change in the accelerator-pedal position is detected, the beginning of the immediately following induction stroke is awaited, whereupon the position of the throttle flap is adjusted to the value specified by the accelerator-pedal position, taking into account the current operating parameters.
Another method in which the adjustment of an air-flow controlling element is delayed relative to the time at which a demand for more fuel occurs is known from U.S. Pat. No. 4,838,223. This is a method for metering additional fuel masses for the purpose of operating additional units, such as an air-conditioning system. When the air-conditioning system is switched on, more air and more fuel must be supplied in order to avoid a break in the speed when idling. A fuel quantity increased by a fixed predetermined value in relation to the case without additional loading is first of all injected and only then is the idle bypass valve opened somewhat further. Only when the torque which can be output has been increased by these measures is the clutch for the air-conditioning system brought into engagement
All methods known to date for adjusting air and fuel masses for a multi-cylinder internal combustion engine lead to driving performances in non-steady-state transitions which are not completely satisfactory. There is therefore the general problem of improving methods of this kind in such a way that driving performance and toxic gas characteristics are better.